Mixed concrete must be placed in a form. A form also often is called a formwork or shuttering. FIG. 2 illustrates a portion of a formwork to produce a square portion of a desired concrete structure. Reference numeral 50 designates a formwork panel that comprises a wood board 51 and a pair of elongated joint members 52 of wood fixed to opposed sides of the board 51 by a suitable method such as nailing. The formwork's square portion of FIG. 2 thus comprises four panels 50. The four panels are also designated by reference numerals P1, P2, P3, and P4, respectively. A first panel P1 and a second panel P2 are connected together with two clamps 100A of this invention. The second panel P2 and a third panel P3 are also similarly connected together with two clamps 100A of this invention. The first panel P1 and a fourth panel P4, however, are connected not by use of clamps of the invention but by nailing a portion 51a of the wood board 51 of the first panel P1 that projects from the wood board 51 of the fourth panel P4, to one of the joint members 52 of the fourth panel P4. This method of connecting the first and fourth panels P1 and P4 is a conventional method employed widely in the prior art, and is much more clearly shown in FIG. 11. The third and fourth panels P3 and P4 are connected together by the same conventional method.
It will be appreciated, however, that all the panels P1 to P4 of FIG. 2 in fact can be connected together either solely by use of the clamps 100A of this invention or solely by the conventional method, although the two methods produce different volumes. As a matter of fact, the formwork's square portion of FIG. 2 is deliberately illustrated as being assembled partly (i.e., at too corners thereof) according to the invention and partly (i.e., at its other two corners) by the conventional method, for the sake of presenting very clearly a difference between the prior art and this invention.
In FIG. 11, reference numeral 60 designates mixed concrete and reference numeral 53 a piece of wood used to chamfer the concrete 60.
Another conventional method (not shown) for connecting formwork panels together at right angles is by nailing together adjacent joint members of adjacent panels.
The conventional technique of nailing formwork panels together to join them, however, has the following drawbacks:
(a) It takes much time and trouble to nail formwork panels together. PA1 (b) The nails can be removed to separate and reuse the panels, but removing the nails takes more time and trouble. PA1 (c) The more often formwork panels are nailed and separated, the sooner they are seriously damaged and, hence, the shorter period of time they only last. PA1 (d) The conventional technique of connecting formwork panels together at right angles, therefore, not only is uneconomical but also conflicts with the spirit of forest conservation. PA1 (e) Damaged formwork panels can be repaired, but to do so naturally involves costs. PA1 (f) Nailing formwork panels together firmly enough requires considerable skill. PA1 (g) Using nails involves a potential danger to the human body.